Antibody against the amino terminus of alpha-actin inhibits actomyosin interactions in the presence of ATP.

Actomyosin interactions in the presence of ATP were examined by using site-specific antibodies directed against the first seven N-terminal residues on skeletal alpha-actin. Fab fragments of these antibodies (S alpha N Fab) inhibited effectively the actin-activated ATPase of myosin subfragment 1 (S-1) at both 5 and 25 degrees C. Binding experiments carried out in the presence of ATP at 5 degrees C revealed that the catalytic inhibition was related to the inhibition of S-1 binding to actin by Fab. At equimolar ratios of Fab to actin, the binding of S-1 to actin and the activated ATPase were inhibited by 75 and 82%, respectively. These results, when contrasted with the small effect of Fab on rigor actomyosin binding, suggest ATP-induced changes at the interface of actin and myosin.

MDM2--master regulator of the p53 tumor suppressor protein.

MDM2 is an oncogene that mainly functions to modulate p53 tumor suppressor activity. In normal cells the MDM2 protein binds to the p53 protein and maintains p53 at low levels by increasing its susceptibility to proteolysis by the 26S proteosome. Immediately after the application of cellular stress, the ability of MDM2 to bind to p53 is blocked or altered in a fashion that prevents MDM2-mediated degradation. As a result, p53 levels rise, causing cell cycle arrest or apoptosis. In this review, we present evidence for the existence of three highly conserved regions (CRs) shared by MDM2 proteins and MDMX proteins of different species. These highly conserved regions encompass residues 42-94 (CR1), 301-329 (CR2), and 444-483 (CR3) on human MDM2. These three domains are respectively important for binding p53, for binding the retinoblastoma protein, and for transferring ubiquitin to p53. This review discusses the major milestones uncovered in MDM2 research during the past 12 years and potential uses of this knowledge in the fight against cancer.

TP53 tumor suppressor protein in normal human fibroblasts does not respond to 837 MHz microwave exposure.

The TP53 tumor suppressor protein (formerly known as p53) responds to a wide variety of environmental insults. To evaluate the safety of cellular telephones, TP53 responses in human fibroblast cells were studied after exposure to 837 MHz microwaves. Cells were exposed in a temperature-controlled transverse electromagnetic (TEM) chamber to a specific absorption rate (SAR) of 0.9 or 9.0 W/kg at 837 MHz continuous-wave (CW) microwave irradiation for 2 h. The TP53 protein levels were measured by Western blot at 2, 8, 24 and 48 h after treatment. The TP53 protein levels in microwave-treated cells, sham-treated cells, and untreated cells remained unchanged relative to each other at all times tested (Fisher test and Student-Newman-Keuls test, P > 0.05). No morphological alterations were observed in microwave-treated cells compared to sham-treated cells. We conclude that TP53 protein expression levels in cultured human fibroblast cells do not change significantly during a 48-h period after exposure to 837 MHz continuous microwaves for 2 h at SAR levels of 0.9 or 9.0 W/kg.

Primary amyloidosis of the trachea.

A case of primary amyloidosis of the trachea in a 40-year-old female is described. It appeared clinically as a tumour-like lesion in the trachea. The specificity of amyloid deposits was confirmed by a positive reaction to Congo red stained sections viewed under polarised light and Thioflavine--T stained section showing characteristic fluorescence. Excision of the lesion with a split thickness graft was the mode of treatment.

Central modulation of croton oil induced subacute inflammation in rats.

Earlier studies from this laboratory have indicated that CNS exerts a modulatory influence over acute inflammation in rats. The present study examines the existence of a similar modulatory effect of CNS on a subacute inflammatory paradigm, the croton oil-induced granuloma pouch in rats. The inflammatory exudate, collected on 6th day after croton oil administration, was found to be substantially less in intracerebroventricular (icv) cannulated and artificial cerebrospinal fluid administered rats as compared to their uncannulated saline (ip) administered counterparts. This effect may be due to stress induced by cannulation. Centrally administered pharmacological agents which attenuate central monoaminergic, cholinergic or prostaglandin systems had insignificant effects on the inflammatory exudate. However, induced increase in central noradrenergic activity was found to attenuate the inflammation when the treatment was done before, but not 48 hr after, the induction of the inflammation. In contrast, induced increase in central serotonergic activity had no effect on the volume of the inflammatory exudate at either time period. Steady state levels of rat brain noradrenaline and serotonin, but not dopamine, were enhanced by the inflammatory procedure. However, these effects may be attributed to the stress induced by croton oil inflammation. The investigation indicates that the modulatory influence of CNS remains limited to the acute phase of inflammation, being exerted mainly by the central noradrenergic system. Once the inflammation has progressed, this modulatory influence of CNS is no longer apparent.

A genital tract peptide epitope vaccine targeting TLR-2 efficiently induces local and systemic CD8+ T cells and protects against herpes simplex virus type 2 challenge.

The next generation of needle-free mucosal vaccines is being rationally designed according to rules that govern the way in which the epitopes are recognized by and stimulate the genital mucosal immune system. We hypothesized that synthetic peptide epitopes extended with an agonist of Toll-like receptor 2 (TLR-2), that are abundantly expressed by dendritic and epithelial cells of the vaginal mucosa, would lead to induction of protective immunity against genital herpes. To test this hypothesis, we intravaginally (IVAG) immunized wild-type B6, TLR-2 (TLR2(-/-)) or myeloid differentiation factor 88 deficient (MyD88(-/-)) mice with a herpes simplex virus type 2 (HSV-2) CD8+ T-cell peptide epitope extended by a palmitic acid moiety (a TLR-2 agonist). IVAG delivery of the lipopeptide generated HSV-2-specific memory CD8+ cytotoxic T cells both locally in the genital tract draining lymph nodes and systemically in the spleen. Moreover, lipopeptide-immunized TLR2(-/-) and MyD88(-/-) mice developed significantly less HSV-specific CD8+ T-cell response, earlier death, faster disease progression, and higher vaginal HSV-2 titers compared to lipopeptide-immunized wild-type B6 mice. IVAG immunization with self-adjuvanting lipid-tailed peptides appears to be a novel mucosal vaccine approach, which has attractive practical and immunological features.

An encephalocele replacing nose completely.

Congenital encephalocele presenting in the nasal region is extremely rare. We present here a case ot tncephaloce lecompletely replacing the nose of a five year old boy and duscuss about similar swellings in this region.

Nucleotide-induced changes in the interaction of myosin subfragment 1 with actin: detection by antibodies against the N-terminal segment of actin.

The binding of myosin subfragment 1 (S-1) to actin in the presence and absence of nucleotides was determined under conditions of partial saturation of actin, up to 80%, by Fab(1-7), the antibodies against the first seven N-terminal residues on actin. In the absence of nucleotides, the binding constant of S-1 to actin (2 x 10(7) M-1) was decreased by 1 order of magnitude by Fab(1-7). The binding of S-1 to actin caused only limited displacement of Fab, and between 30 and 50% of actin appeared to bind both proteins. In the presence of MgAMP.PNP, MgADP, and MgPPi and at low S-1 concentrations, the same antibodies caused a large decrease in the binding of S-1 to actin. However, the binding of S-1.nucleotide to actin in the presence of Fab(1-7) increased cooperatively with the increase in S-1 concentration. Also, in contrast to rigor conditions, there was no indication for the binding of Fab(1-7) and S-1.nucleotide to the same actin molecules. These results show a nucleotide-induced transition in the actomyosin interface, most likely related to the different roles of the N-terminal segment of actin in the binding of S-1 and S-1.nucleotide. The possible implications of these findings to the regulation of actomyosin interactions are discussed.

Actomyosin interactions in the presence of ATP and the N-terminal segment of actin.

The binding of myosin subfragment 1 (S-1) to actin in the presence of ATP and the acto-S-1 ATPase activities of acto-S-1 complexes were determined at 5 degrees C under conditions of partial saturation of actin, up to 90%, by antibodies against the first seven N-terminal residues on actin. The antibodies [Fab(1-7)] inhibited strongly the acto-S-1 ATPase and the binding of S-1 to actin in the presence of ATP at low concentrations of S-1, up to 25 microM. Further increases in S-1 concentration resulted in a partial and cooperative recovery of both the binding of S-1 to actin and the acto-S-1 ATPase while causing only limited displacement of Fab(1-7) from actin. The extent to which the binding and the ATPase activity were recovered depended on the saturation of actin by Fab(1-7). The combined amounts of S-1 and Fab binding to actin suggested that the activation of the myosin ATPase activity was due to actin free of Fab. Examination of the acto-S-1 ATPase activities as a function of S-1 bound to actin at different levels of actin saturation by Fab(1-7) revealed that the antibodies inhibited the activation of the bound myosin. Thus, the binding of antibodies to the N-terminal segment of actin can act to inhibit both the binding of S-1 to actin in the presence of ATP and a catalytic step in ATP hydrolysis by actomyosin. The implications of these results to the regulation of actomyosin interaction are discussed.

Geldanamycin prevents nuclear translocation of mutant p53.

p53 is a tumor suppressor protein that acts in the nucleus to effect cell cycle arrest and apoptosis. In some cells p53 is located in the cytoplasm, perhaps as a means of downregulating its activity. We recently showed that hsp90 forms a complex with the cytoplasmically localized mutant p53 (TSp53vall35) within transformed cells (Sepehrnia et al., J. Biol. Chem. 271, 15084, 1996). The present study was undertaken to determine the p53 conformation bound to hsp90 and the role of hsp90 in p53 nuclear translocation. We show that hsp90 binds both a native and a denatured form of p53 as determined by conformation-specific antibodies. hsp90 does not bind p53 in a spatial-specific manner because it remains bound to p53 when induced to translocate to the nucleus by the protein synthesis inhibitor cycloheximide (CHX). Treatment of transformed cells with geldanamycin (GA), a small molecule that binds hsp90, causes a rapid destabilization of p53 by 50%. Residual p53 that survives GA treatment is incapable of translocating to the nucleus. GA does not destabilize p53 in cells where p53 is genotypically wild type. Although GA appears to dramatically alter the translocating properties of mutant p53 it does not dissociate the p53-hsp90 complex. We suggest that a second chaperone protein, called p23, which we show also binds p53, may play an important role in these GA-mediated effects.